Double interface heat transfer system and snow melting machines employing such a system

ABSTRACT

A process for snow melting but useful elsewhere, accomplished by an air/water interface and a water/snow interface. Water is sprayed into a stream of hot air, which is blown onto the snow. The small particles of water are intimately involved with the air molecules and the heat of the air is absorbed by the water droplets, the air giving up its heat to a very large extent. Next, the droplets are combined into larger drops, and then allowed to drop onto the snow. Water, being much heavier than air is much better at absorbing and carrying heat. The heat of the hot air is thus transferred to the snow causing it to melt by using hot water as a heat transfer medium. If the some of the water turns to steam and condenses back into water the effect is further enhanced by about ten times.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to snow melting machines. More particularly, the invention relates to machines in which a snow melting operation is accomplished by an air/water interface and a water/ice (snow particle) interface.

2. Discussion of the Background

Winter weather in Northern climes brings with it snow and ice, with subsequent inconvenience to road users, users of sports stadia and others. Large amounts of snow need to be removed to make roads passable, parking lots usable and sports fields playable. In intermediate latitudes, it may be possible to simply move snow aside, but in areas where snow fall is heavier and temperatures colder, such as for example in areas prone to lake effect snow, this is not necessarily possible, as the previous snowfall may not have melted. One solution to this problem is to move the snow to a central location and melt it, running the resulting water off to a drain. If you have a pile of snow to melt and you blow hot air or fire on the snow, not much happens, because the hot air will not penetrate directly into the snow, which is a very good insulator, and the air just runs over the surface and dissipates. The invention is directed to an improved solution to this problem.

In the background art, the best known apparatus for melting large amounts of snow is the type of show melting machine manufactured by Trecan. These are believed to be substantially similar in operation to the apparatus shown in FIG. 2. In this arrangement, snow (not shown) to be melted is added to water 430 in a tank 420, the tank 420 having tubes 480 at each corner. The detailed structure of only one tube 480 is shown for clarity. Each tube 480 includes an inner tube 440 and an outer tube 450, as well as a burner 490. The outer tube 450 is provided with lower holes 460 and upper holes 470. Air is blown into each tube 480 by a blower 410 driven by a large diesel engine 400. The air is heated by burner 490 and forced down inner tube 440 into outer tube 450. Water 430 from the tank 420 is admitted into the outer tube 450 via lower holes 460, and a heated mixture of air and water is expelled via upper holes 470 onto the surface of the water 430, so as to melt the snow. A drain 485 is also provided to prevent overflow.

The above-described machine requires a very powerful blower driven by a large engine. This is because the air pressure generated has to overcome the water pressure at the bottom of the tank. Water pressure increases with depth, so the bottom of the tank is where the pressure is greatest. The larger the blower the larger the engine, and the larger the engine the more diesel fuel is consumed by the snow melter. The size of the blower and of the engine also contribute to the size, weight and cost of the snow melter. In addition, the heat transfer is very inefficient, because the time of exposure of the water is limited to that required for the hot air to ascend to the surface of the water bath. This increases the size of the burner as well as the blower and the engine. These and other difficulties of the background art snow melter are overcome by the present invention, as will be described below in relation to the several views, in which like numerals denote like elements.

SUMMARY

This is a description of the advantage of my process devised to use in snow melting machines but useful elsewhere. The operation is accomplished by an air/water interface and a water/ice (snow particle) interface.

In a preferred embodiment of the invention, hot air or fire is incidentally blown on the snow, but water is also sprayed into the stream of hot air/fire. The small particles of water are intimately involved with the air molecules and highly effective heat transfer takes place with the heat of the air being absorbed by an almost infinite number of water droplets. So, then you have lots of hot water droplets and a flow of air that has given up its heat to a very large extent. Next, the droplets are allowed to be combined into large drops or clumps of hot water. The hot water is then allowed to drop onto the snow pile or into a water bath in which the snow has been placed after removal. The water cuts through the snow like a hot knife through butter. The water, being much heavier than air will naturally be much better at absorbing and carrying heat. The heat of the hot air/fire has just been transferred to the snow and caused it to melt by using hot water as a heat transfer medium. The applicant has found that if some of the water turns to steam and condenses back into water the effect is about ten times as good at transmitting the heat as hot water alone would be.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a snow melter according to a preferred embodiment of the invention.

FIG. 2 is an end view of a fuel nozzle disc and fuel delivery pipe according to a preferred embodiment of the invention.

FIG. 3 is a detailed view of part of the snow melter according to FIG. 1.

FIG. 4 is a view of a snow melter according to the background art.

FIG. 5 is a view of a movable snow melting boom according to a preferred embodiment of the invention.

FIG. 6 is a further view of a movable boom and tank according to a preferred embodiment of the invention.

FIG. 7A and FIG. 7B are views of a backflushing filter screen according to a preferred embodiment of the invention.

FIG. 8 is a view of a square ‘snail’ according to a preferred embodiment of the invention.

FIG. 9 is a view of a round ‘snail’ according to a preferred embodiment of the invention.

FIG. 10 is a view of a zig-zag ‘snail’ according to a preferred embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a side view of a snow melting machine according to a preferred embodiment of the invention. In a non-limiting example, the snow melter has a tank 120 that may optionally be provided with wheels 125 to make it easier to move and a hitch 115 for attaching it to a vehicle (not shown) for towing. Tank 120 may be prefilled with water 430, to which snow 135 to be melted is added. A fan 110 draws a flow of air into a conduit 100 and past a fuel jet 180 and an igniter 190. Igniter 190 may, for example, be a common spark plug. Fan 110 may be driven by any suitable means known in the art, such as a diesel engine, electric motor, or the like. The means for driving the fan 110 is not shown. In an alternative embodiment, fuel jet 180 and igniter 190 may be collectively replaced with any suitable commercially available burner. Next, the air passes a water jet 170 which introduces droplets of water to be entrained into the hot air. Water may be supplied to the water jet 170 by any suitable means, such as from the mains water supply, or from the water in the tank by means of a pump (not shown), or by any other suitable means.

Following that the hot air/water mixture passes through a section of conduit 100 provided with baffles 105. Preferably the conduit 100 is round in cross section and the baffles 105 are semi-circular, although this is not apparent from a side view. Other cross-sectional shapes may alternatively be employed without departing from the scope of the invention, for example square or rectangular, although a circular cross section has been found to be preferable. The baffles 105 are shown mounted alternately at the top and bottom of the conduit 100, although they might just as easily be mounted alternately on the right and left sides thereof, for example. The baffles 105 are preferably arranged to overlap slightly at the middle of the conduit 100, sufficiently that no direct path through conduit 100 exists for the mixture without impinging on the baffles 105. Alternatively, leaving a direct path at the center of conduit 100 can reduce back pressure on the fan 110 with only a small loss in heating ability. It will be appreciated by those skilled in the art that other arrangements of baffles are possible without departing from the scope of the invention. The baffles 105 increase the distance to be travelled by the mixture, and slow it down. This gives more time and distance for heat to be exchanged between the water droplets and the air. Not only that, but by impinging on the baffles 105, the water droplets are broken into smaller drops which present more total surface area and so are more effective in melting the snow.

After passing through the baffles 105, the air/water mixture passes from conduit 100 into vertical tube 150. A portion of the mixture goes down the vertical tube or chute 150 to be applied to the surface of the water 430, and a portion is discharged through outlet 160 to be blown onto the surface of the water 430 and onto the snow 135. Both of these portions help to melt the snow 135, the former by raising the temperature and providing agitation of the water 430, and the latter also by spraying hot air and hot water droplets onto the snow 135 to be melted. Note that because vertical tube 150 extends down only to the surface of water 430, instead of almost to the bottom of the tank as in the background art, the water pressure to be overcome is much less, and therefore a small fan 110 can be used in place of the large blower 410 employed in the background art, with concomitant savings in fuel and weight. The level of water 430 in the tank 120 may be controlled, in a non-limiting example, by allowing the water 430 to overflow through drain 145.

The apparatus inside conduit 100 will now be discussed in greater detail in relation to FIG. 2 and FIG. 3. A portion of conduit 100 is shown on a larger scale in FIG. 3, including water jet 170, fuel jet 180 and igniter 190 as shown in FIG. 1. A fuel/air mixture is supplied to fuel jet 180 and is entrained into air drawn into conduit 100 by fan 110. Fuel jet 180 comprises a fuel nozzle disc 200 and a fuel delivery pipe 220, as shown more clearly in FIG. 2. A fuel/air mixture is introduced into fuel nozzle disc 200 via fuel delivery pipe 220, and discharged via exit holes 250.

As shown in FIG. 3, this mixture is then ignited by igniter 190 to create flame zone 320, thereby producing a flow of hot air. 330 is an optional turbine wheel or stationary propellor. Water is introduced into water nozzle 170 via tube 340 and discharged into the stream of hot air at outlet 360. Air is admitted into outlet 360 via holes 350, so as to break the water into droplets. Hot air with entrained water droplets is therefore carried to the next stage of conduit 100 including baffles 105, as described above.

In an alternative embodiment of the invention, as shown in FIG. 5 and FIG. 6, a system embodying the invention is configured to be used to melt a pile of snow 610 in the back of a truck 600 without having to dump the snow into a separate tank. In this arrangement, melt water from the truck 600 is collected in a small tank 520 positioned beneath the tailgate 620 of the truck and pumped by water pump 510 into the base of an water jacket 660 surrounding a vertical column 550. The small tank 520 is provided with a drain tap 530 to drain excess water. Hot air from a conventional oil gun burner 590 as known in the art is supplied to the base of the column 550. At the upper end of the column 550 the water from the water jacket 660 is fed through a water nozzle 670, which may be similar to water nozzle 170 in FIG. 1, and the resulting droplets of water are entrained in the hot air and passed through conduit 500 to outlet 630 which may be directed by hydraulic cylinder 540 to align with the back of the truck 600 to melt the snow. It will be appreciated by those skilled in the art that in place of hydraulic cylinder 540 a pneumatic cylinder or any equivalent means could be employed. Conduit 500 may include baffles similar to the baffles 105 in conduit 100 shown in FIG. 1. The vertical column 550 is supported by rings 640 attached to bearings 680 on mast 650, in turn attached to trailer 560. Optionally, vertical column 550 may also be directed by one or more hydraulic cylinders (not shown). The small tank 520 may be attached to the trailer 560 for convenience.

FIG. 7A and FIG. 7B are views of a backflushing filter screen according to a preferred embodiment of the invention, which may be used, for example, with melt water tank 520 and water pump 510 in the embodiment of FIG. 5 and FIG. 6. FIG. 7A shows the position of the filter during pumping, and FIG. 7B shows the position of the filter during backflushing. Whenever the rate of flow appears to be reduced, the slide ring 700 and screen 710 are raised, thereby opening ports 720 in pipe 750 and allowing water to exit through screen sleeve 710 when pump 510 is reversed, blowing away trash. Bottom blocker 730 keeps the bottom of screen 710 from sucking in trash when pumping. Blocker 730 is hung from the end of pipe 750 on long bolts 760. Any suitable means may be employed to raise and lower the slide ring 700 and the screen 710, as will be apparent to those skilled in the art.

FIG. 8, FIG. 9 and FIG. 10 show alternative structures that may be used, for example, in place of conduit 100 with baffles 105 in FIG. 1. These are meandering structures or ‘snails’ of various shapes, each including a wall 800 provided with projections or ‘speed bumps’ 850 to assist in mixing the heated air and the water. In each ‘snail’ air is introduced at air intake 810 by a fan or blower (not shown) and a burner 890 creates a flame front 820 that heats the air. Water is then introduced through water nozzle 870, and the water is discharged through discharge port 830. The air also exits the same way, except in the embodiment of FIG. 10, where the air exits to the sky through vent 840. FIG. 8 shows a square ‘snail’, FIG. 9 a round ‘snail’ and FIG. 10 a ‘zig-zag snail’. It will, however, be appreciated by those skilled in the art that other shapes are possible without departing from the scope of the invention, as each of these shapes is designed to lengthen the heat exchange path and reduce drop size by mechanical interference.

As can be seen from the foregoing description, each of the embodiments described differ particularly from known snow melters in that water is added to the heated air before it is brought into the tank, truck body, or other vessel or reservoir containing the snow to be melted. Further, in the present invention the water is added to the heated air in the form of droplets from a nozzle, which gives far better heat transfer and residence time than forcing the air up through water, as well as requiring less energy.

As will readily be appreciated by those skilled in the art, numerous modifications and variations of the above embodiments of the present invention are possible without departing from the scope of the invention. 

1. A snow melter, comprising: means configured to discharge heated water droplets onto snow; said water droplets entrained in heated air; wherein: said water droplets are entrained in said heated air before application of said heated air to a vessel containing said snow.
 2. The snow melter according to claim 1, further comprising: a conduit configured to deliver said water droplets entrained in heated air to said vessel; said conduit comprising a plurality of lateral projections; and said lateral projections configured such that said water droplets entrained in heated air impinge on said projections.
 3. The snow melter according to claim 2, wherein: said lateral projections are configured such that no direct path exists through said conduit without impinging on said lateral projections.
 4. The snow melter according to claim 2, wherein: at least a portion of said conduit provided with said lateral projections takes a convoluted path
 5. The snow melter according to claim 1, further comprising: a water nozzle comprising a divergent outlet, said outlet having a plurality of holes in an outer portion thereof; whereby said heated air passes through said plurality of said holes and entrains said water droplets therein.
 6. The snow melter according to claim 1, further comprising: a fuel nozzle disc said fuel nozzle disc comprising a plurality of exit holes arranged around said periphery thereof; said exit holes configured to discharge fuel; and an igniter configured to ignite fuel discharged from said fuel nozzle disc; whereby: air is thereby heated before entraining said water droplets in said air.
 7. The snow melter according to claim 1, further comprising: a pipe carrying said heated air; and a water jacket surrounding said pipe; wherein: said water jacket is provided before a point where said water droplets are entrained in said heated air; and said water droplets comprise water taken from said water jacket after being warmed by said heated air.
 8. The snow melter according to claim 1, further comprising: a discharge outlet for directing said water droplets onto said snow; wherein: said discharge outlet is movable to align it with said vessel containing said snow.
 9. The snow melter according to claim 1, further comprising: a pump for collecting water from the melted snow and providing a supply of water for said water droplets.
 10. The snow melter according to claim 9, further comprising: a filter for filtering said supply of water, said filter comprising: a screen; a pipe comprising a first end communicating with said screen and a second end communicating with said pump; at least one lateral port in said first end of said pipe; a ring configured to close said at least one said lateral port when in a first position and to uncover said at least one said lateral port when in a second position; means to move said ring between said first position and said second position; wherein: said screen covers said at least one lateral port when said ring is in said second position.
 11. A method of melting snow, comprising: discharging heated water droplets onto snow; said water droplets entrained in heated air; wherein: said water droplets are entrained in said heated air before application of said heated air to a vessel containing said snow.
 12. The method of melting snow according to claim 11, further comprising: before delivering said water droplets entrained in heated air to said vessel; impinging said water droplets entrained in heated air on a plurality of lateral projections.
 13. The method of melting snow according to claim 12, wherein: no direct path exists through said conduit without impinging on said lateral projections.
 14. The according to claim 12, further comprising the step of: passing said water droplets entrained in heated air through a convoluted path for at least a portion of said step of impinging said heated air comprising said water droplets on a plurality of lateral projections.
 15. The method of melting snow according to claim 11, further comprising: discharging water into said heated air through a divergent outlet, said outlet having a plurality of holes in an outer portion thereof; whereby said heated air passes through said plurality of said holes and entrains said water droplets therein.
 16. The method of melting snow according to claim 11, further comprising the steps of: discharging fuel through a plurality of radially arranged exit holes; igniting fuel discharged from said radially arranged exit holes; and thereby heating air before entraining said water droplets in said air.
 17. The method of melting snow according to claim 11, further comprising the steps of: providing a pipe carrying said heated air; and providing a water jacket surrounding said pipe; wherein: said water jacket is provided before a point where said water droplets are entrained in said heated air; and pre-heating water in said water jacket, and thereby pre-heating said water droplets, by said heated air.
 18. The method of melting snow according to claim 11, further comprising the steps of: providing a discharge outlet for directing said water droplets onto said snow; wherein: moving said discharge outlet is to align it with said vessel containing said snow.
 19. The method of melting snow according to claim 11, further comprising the steps of: collecting water from the melted snow; and providing a supply of water for said water droplets from said melted snow.
 20. The method of melting snow according to claim 19, further comprising the steps of: providing a filter comprising a screen; opening a first end of a pipe communicating with said screen, said pipe comprising a second end communicating with said pump; closing each of at least one lateral port in said pipe; and filtering said supply of water; and backflushing said filter by the steps of: closing said first end of said pipe; opening at least one said lateral port; and covering said at least one lateral port with said screen. 